1. Field of the Disclosure
This disclosure relates generally to articulators for snowplow blades and, more specifically, to snowplow blade articulators having a passive downforce mechanism.
2. Related Technology
Generally speaking, snowplow blade assemblies come in two different types, an assembly having a straight blade and an assembly having an adjustable or V-blade. The straight blade generally extends across the front of a vehicle, such as a truck. Some straight blades may be angularly adjustable relative to the longitudinal axis of the vehicle. For example, some straight blades may have the capability to angle the straight blade relative to the longitudinal axis of the vehicle to the left or to the right.
V-blades are formed by two wings or blades (a driver's side blade or left wing, and a passenger's side blade or right wing) that meet at a center hinge. Each blade may be independently adjustable relative to the longitudinal axis of the vehicle. As a result, the V-blade may have multiple useful configurations. For example, the V-blade may take on a V-shape with each blade extending at an angle from the center hinge, rearwardly toward the vehicle. The V-blade may also take on an inverted V-shape or scoop configuration, where each blade extends at an angle forward from the center hinge, away from the vehicle. Finally, the V-blade may mimic a straight blade by having one blade extend forward from the center hinge and another blade extending rearward from the center hinge. As a result of the different configurations, the V-blade is known to be generally more adaptable to unique plow areas, especially confined plow areas.
Most snowplow blade assemblies include hydraulically or manually operated articulators for lowering and raising the snowplow blade. These articulators, especially the hydraulically actuated articulators, may also include mechanisms for adjusting an angle of the snowplow blade relative to a vehicle longitudinal axis. Some articulators may also be capable of adjusting portions of the snow plow blade relative to other portions of the snowplow blade, for example, different wings of a V-blade. Generally speaking, hydraulically actuated snowplow blade articulators use hydraulic force to raise the snowplow blade off of the ground when not in use. These articulators remove hydraulic pressure to lower the snowplow blade to the ground for plowing snow. When the snowplow blade is lowered to the ground for plowing snow, the weight of the snowplow blade keeps it on the ground.
In practice, plowing areas are rarely flat and level. To the contrary, most plowing areas have uneven terrain and even obstacles extending upward from the plowing surface, such as curbs, manhole covers, reflectors, ADA-mandated tactile warning tiles, and other objects. Snowplow blades must have the capability to adjust to the uneven terrain and to overcome the obstacles without breaking the obstacle or the blade. Generally speaking, hydraulically actuated snowplow blades are placed in a “float” mode in which hydraulic fluid pressure is removed from the articulator and the weight of the snowplow blade is depended upon to keep the snowplow blade in contact with the plowing surface. However, during certain environmental conditions, such as heavy wet snow, or ice laden snow, the weight of the snowplow blade may not be sufficient to keep the snowplow blade in contact with the plowing surface and the snowplow blade may ride up over the heavy snow or ice. This problem is especially prevalent with lightweight snowplow blades that are mounted on small trucks or utility vehicles.
In an attempt to overcome this problem, some hydraulic articulators have included a hydraulic lock, which locks the snowplow blade in the down position. However, when hydraulically locking the snowplow blade in the down position, the snowplow blade is not capable of moving over small obstacles or adjusting to uneven terrain. As a result, this hydraulic downlock is only beneficial in certain narrow conditions, for example, when plowing nearly level and obstacle free surfaces.
An active downforce mechanism has been used to overcome this problem. One example of an active downforce mechanism is disclosed in U.S. Pat. No. 5,897,786, which is hereby incorporated by reference herein. The disclosed active downforce mechanism includes a pressure switch, which senses pressure in a hydraulic cylinder. When the pressure drops below a certain level, such as when the snowplow blade drops into a recess in the plowing surface, the pressure switch activates a hydraulic pump to supply additional hydraulic fluid pressure. When the pressure rises above a certain level, a pressure relief valve vents excess hydraulic fluid to a reservoir to relieve the pressure. While this active downforce mechanism is effective in providing additional force to the snowplow blade to keep it in contact with the plowing surface, the constant actuation of the hydraulic pump often results in premature pump failure. Moreover, impact forces are transmitted through the hydraulic system and through the mounting hardware directly to the vehicle, where the operator is subject to the same impact forces, before the active downforce mechanism can react and raise or lower the hydraulic pressure.